Which Tracks Benefit from Linear Phase HPFs (and Which Don’t)?
When mixing, one of the most common cleanup moves is to apply a high-pass filter (HPF) to remove unwanted low-end rumble. But not all HPFs are created equal: some EQs let you choose between minimum-phase and linear-phase filtering. This raises the question: Which Tracks Benefit from Linear Phase HPFs (and Which Don’t)?
Let’s break it down in detail.
What’s the Difference Between Minimum-Phase and Linear-Phase HPFs?
- Minimum-Phase HPF: This is the default in most EQs. It removes low frequencies but shifts the phase of nearby frequencies. That phase shift is usually small and often not audible, especially at very low frequencies.
- Linear-Phase HPF: Designed to preserve phase relationships across the frequency spectrum. This avoids any smearing or phase rotation — but comes with latency, higher CPU load, and sometimes pre-ringing artifacts.
In short: linear-phase filters are great for precision, but not always necessary.
Tracks That Benefit from Linear Phase HPFs
1. Full Mix / Master Bus
Applying a gentle linear-phase HPF around 25–35 Hz can clean up subsonic rumble without shifting the audible bass. Since everything passes through the master bus, keeping the phase intact here matters.
2. Parallel Busses (e.g., Drum Crush, Parallel Compression)
When blending processed and dry signals, phase coherence is crucial. A linear-phase HPF ensures both versions of the signal stay aligned, avoiding comb-filtering or hollow low end.
3. Layered Low-End Sources (Kick + Sub-Bass)
If your kick and sub-bass are tightly stacked in the sub frequencies, linear-phase filters help them stay phase-aligned. This ensures the low end feels solid instead of smeared.
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4. Kick and Bass Individually
- Linear phase: Useful if both instruments occupy the same sub frequency region and you want maximum clarity.
- Minimum phase: Often just fine — the slight phase shift can even make the bass feel tighter. Many engineers prefer it for a more musical, less clinical result.
5. Acoustic Instruments (Vocals, Guitar, Piano, etc.)
If you’re just rolling off subsonic noise below 40 Hz, minimum-phase EQ usually works perfectly. The audible difference is minimal, and you save on latency.
Tracks That Don’t Really Need Linear Phase HPFs
6. Non-Bass Percussion (Snare, Hats, Toms)
Phase relationships below 50 Hz don’t really matter here. A minimum-phase HPF will clean up rumble without any drawbacks.
7. Pads, Synths, and Textures
Unless they’re layered with bass-heavy elements where alignment matters, linear phase adds little benefit. Minimum-phase filters are faster and easier on your CPU.
8. Transient-Heavy Tracks During Production
When you’re still recording MIDI drums or playing synth parts live, the latency from linear-phase EQs can throw off your groove. Stick to minimum-phase while creating, then swap later if needed.
Rule of Thumb
- Creative Stage: Use minimum-phase HPFs on individual tracks. They’re fast, zero-latency, and sound good enough for most purposes.
- Mix/Master Stage: Reach for linear-phase HPFs only when phase integrity across low-end elements is critical (master bus, parallel processing, layered subs).
Final Thoughts
Linear-phase EQs are powerful, but they’re not a default setting. Think of them as a specialist tool rather than a catch-all solution. For most tracks, a good minimum-phase HPF will do the job cleanly, quickly, and musically. Save the linear-phase moves for when you truly need surgical precision in the low end.
What about you? Do you reach for linear-phase HPFs often, or do you stick with minimum-phase unless absolutely necessary? Share your thoughts in the comments!
